The invention relates to an elastic pad, especially under-rail. made from elastic plastic or rubber, being used mainly in permanent ways of rail transport as an element attenuating vibrations and absorbing dynamic loads transmitted by vehicles to rails.
There are known many design solutions of elastic under-rail pads of a general rectangular flat shape, made from plastic or rubber, used in rail transport permanent ways as an element attenuating vibrations and absorbing dynamic loads. Every plastic under-rail pad has two opposite sides, one of them designed to overlie the upper face of a rail foundation member or the upper face of a metal bearing plate and the other side designed to underlie the lower face of a rail foot or the lower face of a metal washer. One or two opposite sides of the pads are provided with different profiles such as grooves, posts and other projections to improve dynamic properties of the elastic under-rail pads and to reduce dynamic surpluses transmitted to a rail foundation.
There is known from German patent specification No. 865147 an elastic under-rail pad consisting of a thin middle plate and regularly spaced on the plate opposite projections projecting at both sides of this thin middle plate, the projections having circular or the like cross-section.
There is known from French patent specification No. 1211567 an elastic under-rail pad having at its two main sides many cylindrical projections or projections in the form of a truncated cone, spaced regularly, on these two sides in such a way that projections at one side are directly opposite projections of the other side of the pad.
There is known from British patent specification No. 946936 an elastic under-rail pad having a number of separate areas bearing load, being in the form of truncated hexagonal projections shaped as a pyramid, which are on both opposite sides of the pad and are separated from one another with grooves of the V letter shape. The hexagonal projections on the opposite sides of the pad are directly opposite one another. In particular embodiments of the pad the projections on one side of the pad are rounded, conical or flat.
There is known from European patent specification No. 169685 an elastic under-rail pad consisting of a membrane made from an elastic material, for example from natural rubber, and of projections of stud-like shape projecting in opposite directions at both main sides of the pad. These stud-like projections having generally cylindrical shape are of the same size and evenly spaced across both sides of the pad.
There is known from U.S. Pat. No. 4648554 and European patent application No. 279094 an elastic under-rail pad comprising many spaced apart circular dimples formed on opposite sides of the pad. Centres of said circular dimples formed on one side of the under-rail pad are offset parallelly in lateral direction relative to the centres of the circular dimples formed on the opposite side of the pad so that the pads form is a network of interlock arch bridge portions when said pad is viewed in cross-section. Each of most circular dimples on one side of the pad lies between four dimples situated on the opposite side of the pad.
There is also known from U.S. Pat. No. 4,971,247 an elastic under-rail pad having projections in the form of separate islands, for example chevron-shaped, on one side or on both opposite sides.
There is also known from U.S. Pat. No. 5,195,679 an elastic under-rail pad having protrusions which are offset on one side of the pad relating to protrusions on the other side of the pad so that when the pad is horizontal no vertical line passes through more than one protrusion. Each protrusion is a separated island and it has its end face of circular or rectangular shape. The protrusions are short cylinders or elongated rectangular prisms.
There is also known from U.S. Pat. No. 5,335,850 an elastic under-rail pad consisting of a central core and many regularly spaced studs projecting at both opposite sides of the core. The studs have two different heights and are offset to one another in such a way that the higher studs on the first side of the pad are opposed by the lower studs on the other side of the pad and the lower studs on the first side of the pad are opposed by the higher studs on the other side. All studs are free standing without interconnection therebetween above said core and have encircling sidewalls of outward convex curvature.
An elastic pad according to the invention, made from elastic plastic or rubber, having two opposite sides is characterized in that at least one of its opposite sides is a surface which at least partly is defined at least approximately by a simple and/or composite trigonometric sinusoidal and/or cosinusoidal function so that at least on a part of one of two opposite sides of the elastic pad there are made protrusions and cavities arranged alternately and changing softly one into another.
It is advantageous if at least on one of opposite sides of the elastic pad at least a part of all protrusions are rolls and at least a part of all cavities are grooves, the rolls and grooves are arranged alternately forming a wavy surface. The rolls and grooves run together side by side along straight lines and/or curves.
It is also advantageous if at least on one of opposite sides of the elastic pad according to the invention, at least a part of all protrusions are cupolas and at least a part of all cavities are bowls while each cupola is surrounded by four adjacent bowls and four adjacent surface fragments of saddle shape, the four bowls and four surface fragments of saddle shape are arranged alternately, also each bowl is surrounded by four adjacent cupolas and four adjacent surface fragments of saddle shape, the four cupolas and four surface fragments of saddle shape are arranged alternately.
The invention ensures to get very effective elastic pads, especially under-rail. During passage of a rail vehicle the elastic pad according to the invention distorts mildly and softly that is why it well attenuates vibrations and absorbs impacts emerging during rolling of rail vehicle wheels on a fragment of the rail lying directly on this pad. The elastic pad, according to the invention, does not shift relating to the lower surface of a rail foot and/or the upper surface of a sleeper, so it does not slip out of the gap between a rail foot and a sleeper, what prevents abrasive wear of the sleeper in its under-rail part and also protects the elastic pad according to the invention, against wearing. During compression of the elastic pad according to the invention, in no its point there is a concentration of stresses and the material of protrusions transfers softly and freely, filling up cavities progressively.